Explosion pressures and/or heat and smoke venting units



Aug. 29, 1967 w. E. mm; 3,337,991

EKELOSIGN PRESSURES AND/OR HEAT AND SMOKE VENTING UNITS Filed Oct: 14, 1965 3 Sheets-Sheet 1 z r l 46 28 1 N VEN TOR.

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ATMFIVEY W. E. ADAMS Aug. 29, 1967 EXPLOSION PRESSURES AND/OR HEAT AND SMOKE VENTING UNITS 3 Sheets-Sheet 2 Filed Oct. 14, 1965 INVENTOR.

W/LL/AM E ADAMS BY Aug. 29, 1967 w. E. ADAMS 3,

- EXPLOSION PRESSURES AND/OR HEAT AND SMOKE VENTING UNITS Filed Oct. 14, 1965 5 Sheets-Sheet 3 INVENTOR. W/LL/4M E ADAMS BY @&

ATTORNEY United States Patent 3,337,991 EXPLOSION PRESSURES AND/OR HEAT AND SMOKE VENTING UNITS William E. Adams, Wexford, Pa., assignor to H. H.

Robertson Company, Pittsburgh, Pa., a corporation of Pennsylvania Filed Oct. 14, 1965, Ser. No. 496,112 Claims. (Cl. 49-3) ABSTRACT OF THE DISCLOSURE A venting unit capable of quickly relieving heat and smoke due to fires and shock waves due to explosions occurring in the interior of a building. The venting unit has at least one damper biased in an open position but which is normally closed. Improved releasable means is operable to release the damper for movement to the open position: (1) by means responsive to a preselected elevated temperature within the building; (2) by means responsive to a pressure surge which exceeds a preselected pressure level within the building; and (3) by means which are manually controlled by mechanical linkages from a position within the building.

This invention relates to venting units, and more particularly to venting units for discharging explosion pressures and/or heat and smoke from the interior of a building which are generated as a result of an explosion and/ or a fire.

When a fire or an explosion occurs within a building, a quick relief of the heat and smoke or shock waves (explosion pressures) is necessary in order to minimize damage to the building. Normally, the most convenient discharge point is through an opening provided in the roof of the building. Consequently, venting units have been devised having normally closed dampers which open quickly to discharge the explosion pressures or heat and smoke associated with an explosion or a fire.

These venting units have several disadvantages which the present invention overcomes. For example, in one such prior art venting unit it appears necessary that both dampers be closed simultaneously. It therefore is necessary to have a workman within the building as well as a workman on the roof of the building in order to close the venting unit. Furthermore, the prior art venting units are not completely reliable inasmuch as occasionally one or both of the dampers fails to open when the venting unit is triggered by a fire or an explosion. The unreliability of these units may be traced to the relatively complex release mechanism employed therein.

The venting unit comprises a housing having at least one and preferably two spaced discharge openings each covered with a damper. The dampers are pivotally supported on the housing for movement between a closed position wherein the damper is in sealed engagement with the periphery of the discharge opening and an open position wherein the damper is spaced from the discharge opening to permit free discharge of explosion pressures and/ or heat and smoke. A latch arm is pivotally connected to each damper for movement in unison therewith. The present invention resides in an improved means for releasably and independently retaining each latch arm and hence each damper in the aforesaid normally closed position. The releasable means of the invention is operable to release the latch arms and hence the dampers for movement to the open position 1) by means responsive to a preselected elevated temperature occurring within a building as, for example, a result of a fire; (2) by means responsive to a pressure surge which exceeds a preselected pressure level, the pressure surge being produced by an explosion; and (3) by means which are manually controlled by mechanical linkages.

As an overall object, the present invention seeks to provide improvements in venting units capable of automatic operation for discharging from the interior of a building the heat and smoke resulting from a fire as well as the explosion pressures generated by an explosion.

Another object of the. invention is to provide an improved release mechanism which positively retains the dampers in sealed engagement with the periphery of the discharge openings but which will quickly release the dampers for movement to the aforesaid open position in the event of a fire or explosion.

Still another object of the invention is to provide an improved release mechanism which is operable by temperature responsive and pressure responsive means.

A further object of the invention is to provide a venting unit incorporating the release mechanism of the invention which venting unit is relatively less expensive to manufacture.

A still further object of the invention is to provide an improved release mechanism which is a unitary structure capable of being factory assembled and therefore may be shipped in a ready-to-use assembled condition.

A further object of the invention is to provide an improved release mechanism which permits either one of the dampers to be opened manually and independently of the other damper without effecting the thermal responsive and pressure responsive actuating means.

Still another object of the invention is to provide single means for effectively sealing the discharge openings and for allowing each damper to undergo a slight amount of 'overtravel to insure positive engagement between the latch arms and the releasable retaining means.

The above and other objects and advantages of the present invention will become apparent from the following detailed description by reference to the accompanying drawings, in which:

FIGURE 1 is an isometric view, with portions cut away to show details, of a preferred arrangement of the venting unit of the invention;

FIG. 2 is a plan View of the venting unit (closed) of FIG. 1;

FIG. 3 is a cross-sectional view, taken along the line IlI-III of FIG. 2, illustrating the internal construction of the present venting unit and the release mechanism incorporated therein;

FIG. 4 is a cross-sectional view, taken along the line IVIV of FIG. 3, further illustrating the release mechanism;

FIG. 5 is an isometric view of the present release mechanism;

FIG. 6 is a cross-sectional view, taken along the line VI-VI of FIG. 4, illustrating the release mechanism in its normal latch arm retaining position;

FIG. 7 is a cross-sectional view, similar to FIG. 6, illustrating the operation of the release mechanism when activated by a fire;

FIG. 8 is a cross-sectional view, similar .to FIG. 6, illustrating the operation of the release mechanism during activation by a pressure surgeas a result of an explosion;

FIG. 9 is a plan view illustrating an alternative arrangement of the present venting unit wherein two units are provided each having a damper associated therewith; and

FIG. 10 is an isometric view of an alternative arrangement of the present release mechanism which is employed in each of the venting units of FIG. 9.

Referring now to FIGS. 1-4, inclusive, there is illustrated a venting unit 20 comprising a-housing 22 projecting upwardly from and surrounding a roof opening 24 in a roof of a building. The housing 22 includes a curb 28, side walls 30, end walls 32 and a central gutter 34. The end walls 32 are polygonal in shape having edges which cooperate with the edges of the side walls 30 and the edges of the central gutter 34 to define spaced, discharge openings 36. The discharge openings 36 are inclined with respect to the roof 26. A readily compressible foamed plastic strip 38 is secured to an extends completely around the peripheral edge of each of the discharge openings 36. The inner surfaces of the side walls 30, end walls 32 and gutter 34 are covered with a suitable insulation material of the type which prevents condensation of moisture, thereby eliminating annoying dripping. Flexible foamed polyurethane is a preferred material for the strip 38.

Dampers 40 are pivotally supported on plates 42 secured to the housing 22. In FIG. 1, the dampers 40 are shown in an open position, that is, spaced from the discharge openings 36. When in the open position, the dampers 40 are preferably vertical and are spaced from the discharge openings 36 by a distance sufficient to permit free discharge of explosion pressures, heat and smoke from the roof openings 24. Each of the dampers 40 is, however, normally disposed in overlying relation with the discharge openings 36, as illustrated by the right-hand damper 40 in FIG. 3. When in a closed position, the dampers 40 compress the strips 38 thereby sealing the discharge openings 36 against the ingress of wind, rain and debris. Suitable thermal insulating 43, such as batts of glass fiber and the like, is secured to the inner face of the dampers 40. Alternatively, the dampers may be formed from translucent materials, such as glassfiber reinforced plastic sheets, thereby additionally providing a convenient skylight.

A latch arm 44 is connected to and movable with each of the dampers 40. Each latch arm 44 has its lower end pivotally connected, as at 46, to a pair of spaced, substantially parallel support members 48 which extend transversely of the housing 22, that is, between the side walls 30. Link arms 50 pivotally connect the latch arms 44 to the dampers 40. Hence, each latch arm 44 and damper 40 connected thereto are movable in unison and reciprocably between the open position illustrated by the left-hand damper 40 of FIG. 3 and the normally closed position illustrated by the right-hand damper 40 of FIG. 3.

As stated above, the dampers 40 will be disposed in the open position illustrated in FIG. 1 when the venting unit 20 is discharging explosion pressures, heat and smoke from a building. Consequently, springs 52 are provided having one of their ends connected to the side walls 30 and the other of their ends connected to the latch arms 44 as best shown in FIGS. 3 and 4. The springs 52 are stretched, that is, placed under tension when the damper 40 is in the normally closed position. When the latch arm 44 is released, in a manner to be described, the tensioned spring 52 will forcibly urge the damper 40 into the open position.

A release mechanism 54 is provided within the housing 22 for individually and releasably retaining the dampers 40 in the normally closed position. The release mechanism 54 is adjustably secured to the support members 48 and is positioned in the arcuate path of travel of the latch arms 44. Consequently, when the dampers 40 are pivoted from the open position to the normally closed position, the latch arms 44 will also pivot in unison therewith into engagement with the release mechanism 54.

As can be seen in FIG. 1, a chain 56 has one end connected to the release mechanism 54 and its other end adjustably connected to an anchor 58 supported on a bracket 60 which, in turn, is secured to the housing 22. The chain 56 contains a thermal responsive triggering mechanism 62 employing a fusible link 64 to maintain a spring 66 under tension. As is known, the fusible link 64 will melt at a preselected elevated temperature, for

example, 175 F. Upon melting of the fusible link 64,

the spring 66 will contract and pull the chain 56 to activate the release mechanism 54, thereby opening the dampers 40. The preselected elevated temperature will, of course, be produced within the venting unit 20 when a fire occurs in the interior of a building and within the region of the venting unit 20.

A second chain 68 also is connected to the release mechanism 54 and extends therefrom into the interior of the building. The second chain 68 is used to manually operate the release mechanism 54 for opening the dampers 40 when desired.

Reference is now directed to FIGS. 5 and 6 wherein the release mechanism 54 is fully illustrated. The release mechanism 54 comprises separable keeper plates 70, 72 and 74.connected to and projecting above a channelshaped base 76. The keeper plate 70 is rigidly secured to a web portion 78 of the base and therefore is stationary. The keeper plates 72, 74, on the other hand, are pivotally connected to the web portion 78 by a right angle lug 80 (FIG. 6) projected through a slot 82 in the web portion 78. The keeper plates 72, 74 are, therefore, movable, that is, pivotal toward and away from a face 84 of the stationary keeper plate 70.

The base 76 also has flanges 79 each provided with elongated openings 79a which permit the base 76 to be secured to the support members 48 and vertically adjustable relative thereto.

Each of the movable keeper plates 72, 74 comprise a: first leg 86 terminating at its upper end in a second leg. 88 which preferably intersects the first leg 86 at an obtuse angle, that is, the second leg 88 is inclined with respect to the web portion 78 of the base 76. Associated with each of the second legs 88 is a V-shaped angle member 90 comprising a first leg portion 92 overlying the upper face of the second leg 88 and a second leg portion 94 which projects upwardly from the first leg portion 92 at an acute angle. The angle member 90 has an edge 96 located at the intersection of the first and second leg portions 92, 94. The edge 96 projects inwardly of the first leg 86 and is normally engaged with the face 84. The edge 96 comprises a projection which maintains the first leg 86 spaced from the stationary keeper plate 70 thereby providing a recess 98 adapted to receive the latch arm 44. In order to guide the latch arm 44 into the recess 98, the stationary keeper plate 70 has an upper end 100 which is inclined and diverges from the inclined second leg portion 90 to provide a trough 102. It should be noted that the inclination of the second leg portion 94 also serves as means for separating the keeper plates 70, 72 and 70, 74 when the latch arms 44 are moved into engagement with the release mechanism 54, that is, when the dampers 40 are being closed.

The keeper plates 70, 72 and 74 are biased into mutual engagement by means of springs 104 carried on bolts 106 each of which extends through both of the keeper plates 70, 72 and 70, 74. During separation of the keeper plates 70, 72 and 70, 74, the springs 104 are compressed between the first legs 84 of the movable keeper plates 72, 74 and washers 108 retained on the bolts 106 by nuts 110. The amount of compression of the springs 104 may, of course, be varied, as desired, by moving the nuts 110 in the appropriate direction relative to the bolts 106.

Each of the angle members 90 is yieldably secured to the movable keeper plates 72, 74 by pairs of spaced springs 112 carried on bolts 114 which extend through and downwardly of the second leg 88 and the first leg portion 92. The pairs of springs 112 are compressible between the lower face of the first leg 88 and washers 116 retained on the bolts 114 by nuts 118. The amount of compression of the springs 112 may, of course, be varied, as desired, by moving the nuts 118 in the appropriate direction relative to the bolts 114.

Several important features arise from the construction of the release mechanism 54 described above. For eX- ample, the keeper plates 70, 72 and 70, 74 are normally biased into mutual engagement. The line of action of the biasing means, that is, the springs 104, is substantially perpendicular to the path of travel of the latch arms. As shown in FIG. 6, the line of action of the spring 104 is horizontal while the path of travel of the latch arm 44 is vertical. Consequently, the required strength of the springs 104 is not dependent on the strength of the springs 52 which forcibly urge the damp ers 40 into the open position. The springs 104 need only be strong enough to maintain the keeper plates 70, 72 and 74 in mutual engagement. Further, because the keeper plates 70, 72 and 74 are substantially parallel to one another and because the first leg portion 92 of the angle member 90 is sloped, the latch arms 44 do not subject the keeper plates 70, 72 and 74 to forces which tend to separate them. Actually, the slope of the first leg portion 92 is such that the movable keeper'plates 72 and 74 are urged toward engagement with the stationary keeper plate 70.

Further, the angle member is yieldably secured to the second leg 88 by means of the springs 112. The line of action of the springs 112 is approximately parallel to the path of travel of the latch arms 44. Therefore, the springs 112 act in opposition to the lifting action of the springs 52. However, the springs 112 do not oppose the entire lifting force of the springs 52 inasmuch as the springs 52 are inclined, for example, with respect to the support members 48. The retractive force of the spring 52 may, as is conventional, be represented by horizontal and vertical force vector components. The springs 112, as can be seen, oppose only the vertical force vector component. Therefore, the size and strength of the springs 112 are considerably less than that of the springs 52. Inasmuch as the line of action of springs 112 is approximately parallel to the path of travel of the latch arms 44, the springs 112 comprise means responsive to a pressure surge acting upwardly against the dampers 40 for separating the keeper plates 70, 72 and 74 to release the latch arms and hence the dampers 40 for movement to the open position as will more fully be described later in the specification.

Reference is now directed to FIG. 7 wherein there is illustrated the release of the latch arm 44 when triggered by a fire. The keeper plates 70 and 72 are shown spaced apart to permit the latch arm 44 to move out of the recess 98 in the direction of the arrow. The separation of the keeper plates 70, 72 is accomplished by the thermal responsive triggering mechanism 62. That is to say, the fusible link 64 (shown broken) has melted releasing the tension in the spring 66 which, in turn, has contracted the chain 56 to effect separation of the keeper plates 70, 72. The spring 66 will, of course, maintain the keeper plates 70, 72 separated until such time as a new fusible link is attached to the triggering mechanism 62.

' Referring now to FIGS. 1 and 7, it will be seen that when desired, the second chain 68 may be pulled to effect separation of the keeper plates 70, 72 and 74 in exactly the same manner as accomplished by the triggering mechanism 62 acting on the first chain 56. The second chain 68 extends into the interior of the building to some convenient location therein. Note also that the release mechanism 54 may be operated manually without affecting the triggering mechanism 62.

FIG. 7 may also be used to illustrate the manner in which the latch arms 44 are engaged in the recess 98. Assume now that the latch arm 44 is moving downwardly instead of upwardly as indicated by the arrow. It will become readily apparent that as the latch arm 44 engages the inclined second leg portion 94 of the angle member 90, the angle member 90 and, hence, the keeper plate 72 Will be subjected. to a lateral force which moves the keeper plate 72 clockwise as shown in FIG. 7. Inasmuch as the springs 104 are relatively weak, insertion of the latch arm 44 into the recess 98 may be accomplished with relatively little fiorce. Now, because of the inclined position of the first leg portion 92 of the angle member 90, the latch arm 44 is required to undergo a slight amount of downward overtravel, that is, through a short distance sufficient to permit the edge 96 to ride over the top of the latch arm 44. This light amount of overtravel is permitted to occur by virtue of the readily compressible property of foamed plastic strip 38 surrounding each of the discharge openings 36. That is, the dampers 40 Will engage the strips 38 and compress the same to provide a seal for the discharge openings 36 as well as to permit the required amount of overtravel. The closing can be quickly accomplished by an operator standing on the roof 26 and pushing the open damper 40 to its closed position where automatic latching occurs.

Reference is now directed to FIG. 8 wherein there is illustrated the manner in which the keeper plates 70, 72 are separated as a result of an explosion occurring Within a building. As is known, an explosion generates shock waves which the explosion. When an explosion occurs within a building, these shock waves radiate to all parts of the room or area of the building in which the explosion has occurred. These shock waves or explosion pressures will impinge on the inner face of the dampers 40 thereby subjecting the dampers to a force which tends to push them out. This force will, of course, be transmitted directly through the link arms 50 to the latch arms 44 which, in turn, causes the angle member to be angularly displaced, as illustrated in FIG. 8. Thereafter, the latch arm 44 will slide past the edge 96 and out through the trough 102. The keeper plate 72 also will move clockwise (FIG. 8) against the force of the springs 104 to facilitate release of the latch arm 44.

Although it is preferred that the venting unit 20 be made with two of the dampers 40 as shown in FIGS. 1-3, inclusive, there may arise instances wherein the desired location of the venting unit and the structural framework or other parts of the building prevent a venting unit, such as the unit 20, to be installed. In this instance it would be desirable to have the venting unit formed in two separate units each having a damper. Such a construction is shown in FIG. 9 wherein there are illustrated two venting units 124A and 124B each comprising a housing 126 surrounding an opening (not visible) in a roof 128 of a building. Each housing is provided with a damper 130 overlying a discharge opening 132 having a readily compressible foamed plastic strip 134 extending completely around its peripheral edge. Each of the dampers 130 are pivotally connected to the housing 126 for movement between the aforementioned open position and normally closed position. Each damper 130 also is provided with an outwardly biased latch arm, such as described above. A release mechanism 136, shown in FIG. 10, is suitably supported within the housing 126 in the path of travel of the latch arm.

The release mechanism 136 is similar to the release mechanism 54 and hence, corresponding numerals will be employed to identify corresponding parts heretofore described.

The release mechanism 136 has a channel-shaped base 138 including a web portion 140 and depending flanges 142. The flanges 142 are provided with slots 144 which permit the release mechanism to be adjustably secured to the support members. Projecting upwardly from the web portion 140 in a single stationary keeper plate 70 and a single movable keeper plate 72. The movable keeper plate 72 is pivotally connected to the web portion for movement toward and away from the stationary keeper plate 70. Spring 108 biases the movable keeper plate 72 into engagement with the stationary keeper plate 70.

The movable keeper plate 72 is identical in construction with the movable keeper plate 72 or 74 of the release mechanism 54. Operation of the release mechanism radiate outwardly of the center of 136 is identical with the ope-ration of the release mechanism 54. That is to say, (1) a thermal responsive triggering mechanism (not shown) will be connected to the movable keeper plate 72 by a first chain; (2) a second chain will also be employed to efiect manual operation of the release mechanism 136 when desired; and (3) the angle member 90 is angularly displaceable by explosion pressures to release the dampers 130 for movement to the open position.

Although the invention has been shown in connection with certain specific embodiments, it will be readily apparent to those skilled in the art that various changes in form and arrangement of parts may be made to suit requirements without departing from the spirit and scope of the invention.

1 claim as my invention:

1. In a venting unit for discharging explosion pressures, heat and smoke, comprising a housing surrounding an opening in a roof of a building and projecting thereabove, said housing having at least one discharge opening, a damper overlying said discharge opening and disposed in sealed engagement with the periphery of said discharge opening, means for pivotally supporting said damper for movement between its normally engaged position and an open position wherein said damper is spaced from said discharge opening by an amount sufficient to permit free discharge of explosion pressures, smoke and heat generated within said building, means for :forcibly urging said damper toward said open position, and mea'ns for releasably retaining said damper in sealed engagement with the periphery of said discharge opening, the improvement in said releasable retaining means comprising:

a latch arm connected to said damper ment therewith;

separable keeper plates biased into mutual engagement and positioned to receive therebetween and releasably retained said latch arm;

means-responsive to a preselected elevated temperature within said building for separating said keeper plates to release said latch arm and hence said damper for movement to said open position; and

means responsive to a pressure surge within said building and above a preselected pressure level for sepa-rating said keeper plates to release said latch arm and hence said damper for movement to said open position.

2. The improvement as defined in claim 1 wherein a readily compressible foamed plastic strip extends completely around the periphery of each of said discharge openings, said strip being compressed by said dampers and thereby sealing each of said discharge openings, and accommodating overtravel of said latch arm between said keeper plates.

3. The improvement of claim 1 wherein the said latch arm is pivotally supported at one end thereof for movement in the direction of movement of said damper and including means for pivotally connecting said latch arm to said damper.

4. The improvement as defined in claim 1 having a support member within said discharge opening wherein said releasable keeper plates comprise:

a stationary plate supported by said support member;

a mlovable plate adjacent to a face of said stationary p ate;

means for supporting said movable plate for movement toward and away from said face;

a projection on the free end of said movable plate, said projection maintaining said movable plate spaced from said stationary plate and being engaged by said latch arm to retain the same between said movable plate and said stationary plate; and

means for biasing said movable plate toward said stationary plate and hence said projection into engagement with said face.

for pivotal move- 5. The improvement as defined in claim 4 wherein the line of action of said biasing means is substantially per-.

6. The improvement as defined in claim 1 having a support member Within said discharge opening wherein said releasable keeper plates comprise:

a stationary plate supported by said support member;

a movable plate positioned adjacent to a face of said stationary plate;

an outturned flange on the free end of said movable plate extended away from said stationary plate; an angle member overlying said outturned flange and having an edge displaced inwardly of said movable plate and engaged with said face of said stationary plate; 7

said movable plate and angle member cooperating with said face to define a recess into which said latoh arm resides when said damper is closed;

means for biasing said movable plate toward said stationary plate and hence said edgeinto engagement with said face; and

means for yieldably connecting said angle member to said outturned flange whereby said angle member is vangularly displaceable relative to said outturned flange in the direction of movement of said latch arm.

7; The improvement as defined in claim 6 wherein the line of action of said yieldable connecting means is generally parallel to the direction of movement of said latch arm.

8. The improvement as defined in claim 6 wherein said angle member and said stationary plate have adjacent diverging upper end portions defining a trough for guiding said latch arm into said recess.

9. The improvement as defined in claim 1 including means operatively connected to said separable keeper plates and extending into the interior of said building for manually separating said keeper plates.

10. In a venting unit for discharging explosion pressures and/or heat and smoke, comprising a housing surrounding an opening in a roof of a building and projecting thereabove, said housing having spaced discharge openings, dampers one each overlying each discharge opening and being normally disposed in sealed engagement with the periphery of the discharge opening, means for pivotally supporting each of said dampers for movement between its normally sealed engagement and an open position wherein the dampers are spaced from the discharge openings by a distance suflicient to permit free discharge of explosion pressures, heat and smoke generated within said building, means for forcibly urging each damper toward said open position and, means for releasably retaining each of said dampers in sealing engagement with the periphery of its corresponding diSe charge opening, the improvement in said releasable retaining means comprising:

latch arms, one each for each of said dampers; means adjacent to the pivotal edges of said dampers for individually and pivotally supporting each of said latch arms; means for pivotally connecting each of said latch arms to an adjacent one of said dampers; said latch arms being independently pivotal toward and away from each other in unison with the adjacent 9 10 means responsive to a pressure surge generated Within 2,827,003 3/1958 Stetson 49379 X said building and above a preselected pressure level 2,940,377 6/1960 Darnell et a1. 49110 X for separating said keeper plates to release said latch 3,182,581 5/1965 Von Poederoyen et a1. 498 X arms and hence said dampers :for movement to said open position. 5 DAVID J. WILLLAMOWSKY, Primary Examiner.

References cued HARRISON R. MOSELEY, Examiner.

UNITED STATES PATENTS 435,597 9/1890 Walder 292 124 I. KARL BELL, Asszstam Examiner. 

1. IN A VENTING UNIT FOR DISCHARGING EXPLOSION PRESSURES, HEAT AN SMOKE, COMPRISING A HOUSING SURROUNDING AN OPENING IN A ROOF OF A BUILDING AND PROJECTING THEREABOVE, SAID HOUSING HAVING AT LEAST ONE DISCHARGE OPENING, A DAMPER OVERLYING SAID DISCHARGE OPENING AND DISPOSED IN SEALED ENGAGEMENT WITH THE PERIPHERY OF SAID DISCHARGE OPENING, MEANS FOR PIVOTALLY SUPPORTING SAID DAMPER FOR MOVEMENT BETWEEN ITS NORMALLY ENGAGED POSITION AND AN OPEN POSITION WHEREIN SAID DAMPER IS SPACED FROM SAID DISCHARGE OPENING BY AN AMOUNT SUFFICIENT TO PERMIT FREE DISCHARGE OF EXPLOSION PRESSURES, SMOKE AND HEAT GENERATED WITHIN SAID BUILDING, MEANS FOR FORCIBLY URGING SAID DAMPER TOWARD SAID OPEN POSITION, AND MEANS FOR RELEASABLY RETAINING SAID DAMPER IN SEALED ENGAGEMENT WITH THE PERIPHERY OF SAID DISCHARGE OPENING, THE IMPROVEMENT IN SAID RELEASABLE RETAINING MEANS COMPRISING: A LATCH ARM CONNECTED TO SAID DAMPER FOR PIVOTAL MOVEMENT THEREWITH; SEPARABLE KEEPER PLATES BIASED INTO MUTUAL ENGAGEMENT AND POSITIONED TO RECEIVE THEREBETWEEN AND RELEASABLY RETAINED SAID LATCH ARM; MEANS RESPONSIVE TO A PRESELECTED ELEVATED TEMPERATURE WITHIN SAID BUILDING FOR SEPARATING SAID KEEPER PLATES TO RELEASE SAID LATCH ARM AND HENCE SAID DAMPER FOR MOVEMENT TO SAID OPEN POSITION; AND MEANS RESPONSIVE TO A PRESSURE SURGE WITHIN SAID BUILDING AND ABOVE A PRESELECTED PRESSURE LEVEL FOR SEPARATING SAID KEEPER PLATES TO RELEASE SAID LATCH ARM AND HENCE SAID DAMPER FOR MOVEMENT TO SAID OPEN POSITION. 